vpn for ios let's you browse websites that may be blocked depending on the location from where you are accessing the internet. For example if you are somewhere where some websites may be censored by local authorities, the vpn will let you access the blocked content by connecting you to a location that can access that content.
In addition, the free tool can also block system-wide ads as well as trackers, for free. Opera does collect data for statistical purposes and may send limited push notifications with marketing material (if you turn off the notifications for the app, the vpn won't work). Currently there are 5 vpn access locations in Cananda, Netherlands, Germany, Singapore and the US. which are hosted by SurfEasy which recently has been acquired by Opera.
The vpn option has already been integrated into the desktop version of the Opera web browser for Windows as well as OS X. As this is a free service you may not agree with the terms or you may prefer more options and features. If that's the case, witopia has been offering reliable and good vpn services for quite a long time and well worth the cost.